/**
 * Keafmd
 *
 * @ClassName: Demo
 * @Description: Demo
 * @author: lijl
 * @date: 2022/11/25 14:45
 * @Blog: https://keafmd.blog.csdn.net/
 */
interface IShape{
    double area();
}
class square implements IShape{
    private double a;
    square(double a){
        this.a = a;
    }
    @Override
    public double area() {
        return a * a;
    }
}
public class Demo {
    public static void main(String[] args) {
        square s = new square(2);
        System.out.println(s.area());
    }
}
